1. Field of the Invention
The present invention relates to a bearing arrangement for supporting a neck of a roll of a rolling mill stand.
2. Description of the Prior Art
The prior art discloses a number of bearing arrangements for rolls of rolling mill stands. Thus, German Patent DE 1 254 108 discloses a bearing arrangement in which an axial bearing rotatably supports a neck of a roll. A circular nut, which is screwed on a neck extension provided with an outer thread, fixes the axial bearing in the axial direction. The fixation is effected with a circular shoulder of the circular nut that presses the axial bearing against a stop in form of a sleeve ring. The circular nut has an outer circular shoulder for interaction with a circular shoulder of a housing ring of the axial bearing upon a reverse rotation of the circular nut for dismounting of the axial bearing from the roll neck. Thereby, the axial bearing is mechanically released by axial forces transmitted by the thread. For releasing the nut traditionally a crane cable is used, which is dubious, however, from a technical point of view. Besides, with release or mounting of the nut with a crane cable, axial forces applied to the axial bearing by the circular nut or its circular shoulder, cannot be precisely adjusted.
In order to avoid the above-mentioned drawbacks, for some time, another bearing arrangement is used which is shown in FIG. 3 (see “New Developments for a More Cost-Effective Application of Morgoil-Bearings in Modern Flat Rolling Mills” by K. Roeingh and W. Scheffel, reprint of a paper presented at SARUC 2000 Conference in Vanderbijlpark, South Africa, on Oct. 5, 2000; presenter-SMS Demag AG, Eduard-Schloemann-Strasse 4, Duesseldorf, Germany). With this bearing arrangement, an axial bearing 110 is secured on a roll neck 210 of a roll 200 with a hydraulic device 120. The hydraulic device 120 has a hydraulic piston 122 and a hydraulic cylinder 124 displaceable relative to each other. The fixation of the bearing 110 is effected by pressing the bearing with the hydraulic cylinder 124 in the direction of roll camber against a stop 30 in form of sleeve ring. The hydraulic piston 122 is supported, in the axial direction, mechanically against the roll neck 210. On the hydraulic piston 122, an outer thread 123 is provided. A circular nut body 132 of a circular nut 130 is screwed on the thread 123. The circular nut serves as a stop for the hydraulic cylinder 124 when it is pressed against the circular nut 130 as a result of application of axial forces which can be generated during operation of the roll.
Very large axial forces, which are generated during a rolling process in the form of an inclined take-off force that, with a radially acting rolling force, total separating force TSF/2, acts, as a partial component of the rolling force, on a conical portion 210a of the roll neck 210. This inclined take-off force FH is transmitted to the roll neck 210 by the neck sleeve 320, the opposite stop, i.e., the sleeve ring 300, the axial bearing 110, the hydraulic cylinder 124, the circular nut 130, and the hydraulic piston 122. In addition to the inclined take-off force FH, an additional axial force component is generated at a so-called cross-rolling, i.e., at joggling of the rolls. This axial force component can act in the same direction as the inclined take-off force or in the opposite direction. The sum of the inclined take-off force, which is generated as a result of cross-rolling, will be referred to simply as axial force.
The axial force, if it is not absorbed, as will be described, in the following sentence, causes displacement of the axial bearing 110 and the hydraulic cylinder 124 away from the roll. However, the axial force is absorbed by the circular nut 130 which, in turn, is supported, via the outer thread 123 of the hydraulic piston 122, against the hydraulic piston 122 that, in turn, is supported against the roll neck 210. In this way, the axial force is transmitted to the roll neck and is absorbed thereby.
As a result of the hydraulic cylinder 124 being pressed, without being actuated, by axial forces against the circular nut 130, the nut 130 is pushed back, as shown in FIG. 4. This is disadvantageous. The reverse push means that a bending or reverse torque acts on the nut, which results in that the nut partially looses contact with the outer thread on which the nut is screwed on. This means that the contact surface of a thread pitch between the circular nut and the hydraulic piston 122 is reduced. This again results in the remaining thread contact surface becoming more loaded by the remaining axial force component, which, with time, leads to the distortion of the thread and thereby to the elimination of the ability of the neck roll to absorb the acting axial force.
Proceeding from this state of the art, the object of the invention is to so modify the known bearing arrangement for a roll of a rolling mill stand that transmission of the axial force from the hydraulic cylinder to the hydraulic piston by the circular nut is insured even at large axial forces, i.e., at a large reverse torque produced by the axial forces.